A diode array may be used in semiconductor memory devices. The individual diodes in a given array are typically addressed via bit and word line selection. Resistance of a programmable resistor in series with the selected diode is controlled to select a desired memory state. The presence of a diode improves the switching properties of a programmable resistor by creating a threshold voltage which must be overcome before the memory state can be changed.
One possibility for a programmable resistor is a polymer element in a polymer memory cell. Polymer memory stores data based on the polymer's electrical resistance, rather than encoding zeroes and ones as the amount of charge stored in a cell. A polymer memory cell may have a polymer sandwiched between two electrodes. Application of an electric field to a cell lowers the polymer's resistance, thus increasing its ability to conduct current. The polymer maintains its state until a field of opposite polarity is applied to raise its resistance back to the original level. The different conductivity states represent bits of information. A conjugated polymer memory cell may also have a superionic conductor material layer to supply ions to the polymer and change its state from a high resistance to a low resistance.
Japanese Patent Application Nos. 2000-334686 and JP 2001-138103 describe a point contact array, NOT circuit and electronic circuit with Ag2Se/Cu2Se interfaces between electrodes to reversibly control the conductance between electrodes. Japanese Patent Application No. 2000-265344 refers to an electronic device including a first electrode made of a conductor material having ionic conductors and electron conductors and a second electrode made of a conductive material. A voltage is applied between the first and second electrodes such that the first electrode is negative with respect to the second electrode so that mobile ions move from the first electrode to the second electrode to form a bridge between the electrodes.